James W. Knight

Virginia Tech | VT · Department of Animal & Poultry Sciences

Calorie restriction (CR) provides anti-aging benefits through diverse processes, such as reduced metabolism and growth and increased mitochondrial activity. Although controversy still exists regarding CR-mediated lifespan effects, many researchers are seeking interventions that mimic the effects of CR. Yeast has proven to be a useful model system f...

Consumption of zearalenone (ZEN) detrimentally affects tissues and systems throughout the body, and these deleterious effects are especially pronounced in swine. The objectives of this project were to determine the effects of short-term consumption of ZEN (at concentrations that could be found on-farm) on growth, carcass weight, liver weight and re...

Zearalenone (ZEN) is a potent estrogenic toxin in swine, contributing to economic losses in herds via reproductive consequences such as pelvic organ prolapse (POP). To better understand the relationship between ZEN-consumption and reproductive symptoms, an animal feeding study with pubertal gilts was designed. The gilts were exposed to three differ...

The mycotoxin zearalenone (ZEN) is a common contaminant of swine feed which has been related to a wide range of reproductive anomalies in swine, such as pelvic organ prolapse, anestrous, and pseudopregnancy. New information is needed to understand how ZEN and related metabolites accumulate in swine reproductive tissues. We conducted a feeding study...

In response to acute loss of the Ulp2 SUMO-specific protease, yeast become disomic for chromosome I (ChrI) and ChrXII. Here we report that ChrI disomy, which creates an adaptive advantage in part by increasing the dosage of the Ccr4 deadenylase, was eliminated by extended passaging. Loss of aneuploidy is often accompanied by mutations in essential...

Maternal diet has been shown to impact fetal development across a variety of species. Given the reported effects of omega-3 long-chain polyunsaturated fatty acid (n-3 LCPUFA) supplementation on health across species, it was hypothesized that supplementation of algal-based n-3 LCPUFA to mares around conception would alter the maternal uterine enviro...

Rapid rebreeding of winter- and spring-lambing ewes is essential if ewes are to lamb more than once per year, but fertility of lactating ewes is often low and early weaning of lambs may be undesirable in forage-based production systems. Selection to improve fertility in spring matings has been successful and led to development of ewes with a reduce...

A wide-spread problem with increasing prevalence, obesity among horses is associated with equine metabolic syndrome and related conditions of insulin resistance and aberrant reproductive cyclicity. The naturally occurring phytoestrogenic stilbene derivative resveratrol has been shown to elicit shifts in physiology of obese animals consuming a high...

Contents Contentious issues and polarized viewpoints can be utilized in the classroom and beyond to create a reflective dialogue among students and citizens. This dialogue leads to both a greater understanding, as well as an enhanced appreciation of alternative viewpoints. Exploring and discussing the scientific, ethical, moral, political, legal an...

Semen characteristics in boars fed organic or inorganic sources of Se were assessed in 3 experiments. Crossbred boars were randomly assigned at weaning to 1 of 3 dietary treatments: I) basal diets with no supplemental Se (control), II) basal diets with 0.3 mg/kg of supplemental Se from an organic source (Sel-Plex, Alltech Inc., Nicholasville, KY),...

An increase in sensitivity of the hypothalamus to negative feedback effects of estradiol results in decreased frequency of gonadotropin releasing hormone and a resultant decrease in secretion of luteinizing hormone (LH) during seasonal anestrus in ewes. This study investigated differences in endocrine profiles associated with timing of hypothalamic...

This study was conducted to evaluate the effects of different concentrations of the antioxidant N-acetyl-cysteine (NAC) supplemented to the maturation medium on porcine embryo development. Concentrations of NAC and its synthetic derivative, NAC-amide (NACA) were evaluated for effects on nuclear maturation, fertilization success and embryo developme...

The mechanisms of oxidative stress in in vitro maturing porcine oocytes and the effects of anti-oxidant supplementation of the medium in ameliorating these effects were investigated in the present study. In addition to intracellular reduced glutathione (GSH) concentrations and DNA fragmentation, the present study focused on superoxide dismutase (SO...

Objectives: To compare pregnancy rate and number of embryos 30 days post mating in gilts group-housed in pens of three and gilts housed individually in gestation stalls. Other potential indicators of swine welfare examined included body weight, backfat thickness, lesions, lameness, display of stereotypies, and serum cortisol concentrations. Methods...

We previously reported that ovulation rate, but not pregnancy rate or litter size at d 30 after mating, was enhanced by treatment with P.G. 600 (400 IU of PMSG and 200 IU of hCG, Intervet America, Inc., Millsboro, DE) in gilts fed the orally active progestin, altrenogest (Matrix, Intervet America, Inc.) to synchronize estrus. We hypothesized that i...

We tested the hypothesis that prostaglandin-F2α (PGF2α) enhances sexual behavior in boars with suppressed testosterone and estradiol secretion. After semen collection at week 0, boars received an s.c. implant containing a gonadotropin-releasing hormone agonist (GnRHa) or were sham-implanted. Beginning at week 1, GnRHa-implanted boars received i.m....

High concentrations of intracellular glutathione (GSH) enhance in vitro production of porcine embryos. Objectives were: (1) to determine the effects of gamma-glutamyl cycle compound supplements to the IVM medium on IVF and IVC; and (2) to evaluate embryo viability. Porcine oocytes were matured in NCSU 23 medium supplemented with either l-cysteine (...

In some species, dietary supplementation with L-carnitine has been reported to increase sperm concentration and sperm motility. The objective of these experiments was to test the hypothesis that L-carnitine supplementation improves the semen characteristics of boars. In Experiment 1, boars (258 days of age) were fed daily a control diet (n = 9) or...

The study was conducted to determine the response of sows to oxidized and reduced forms of supplemental folic acid in the diet. Gilts were mated and fed a standard corn-soybean meal diet with no supplemental folic acid. On d 105 of gestation, gilts were randomly assigned to one of four dietary treatments for the remainder of the study. Treatments w...

Concentrations of leptin in serum and milk were assessed in gilts fed diets during gestation that differed in energy level. Beginning at day 45 and continuing throughout pregnancy, gilts received either a high-energy (6882 kcal metabolizable energy (ME) per day) or low-energy (5221 kcal ME per day) diet (n = 9 per group). All gilts had ad libitum a...

The objective was to determine if i.m. treatments of lutalyse (PGF2alpha; dinoprost tromethamine salt) expedited the training of sexually inexperienced boars for semen collection. Lean-type, terminal-line boars (n = 40; 177.4 +/- 2.4 day of age and 112.8 +/- 2.0 kg body weight) that had not previously experienced natural mating were utilized. Boars...

The effects of naloxone, an antagonist of opioid peptides, on circulating concentrations of luteinizing hormone (LH), testosterone, and growth hormone (GH) were determined in sexually mature boars. Blood samples were collected at 15-min intervals for three hr from five crossbred boars. Two hr after initiation of blood sampling, boars received an i....

Three experiments assessed the onset of estrus and ovulation rate in gilts treated with gonadotropins after the withdrawal of an orally active progestin. In Exp. 1, all cycling gilts received the progestin (Regu-mate; Intervet America Inc., Millsboro, DE) at a rate of 15 mg/d for 18 d. Twenty-four hours after the last feeding of Regu-mate, 32 gilts...

Colostrum and milk are natural vehicles for acquiring passive immunity and are valuable tools for decreasing neonatant mortality from diarrheal disease. The effects of recombinant human protein C (rhPC) expression levels on endogenous immunoglobulin and transferrin content of the milk of different lineages of transgenic pigs were studied. The level...

The mammary gland of transgenic livestock can be used as a bioreactor for producing complex therapeutic proteins. However, the capacity for making a given post-translational modification upon any given polypeptide is uncertain. For example, the efficiency of gamma-carboxylation of glutamic acid in the amino terminal regions of recombinant human pro...

This study was designed to 1) determine milk yield of sows that were machine milked; 2) assess the effects of pulsation rate, pulsation ratio, and pig removal on milk yield; and 3) assess litter weights. In Exp. 1, four sows were milked daily to 60 d postpartum. There were differences (P < .05) in milk yield among sows, the greatest being 1,898 mL/...

This study was conducted to 1) determine milk yield of sows that were machine milked up to four times daily; 2) determine the effect of pig substitution on milk yield; 3) assess litter weight changes for sows that are milked; and 4) determine milk composition. Eight sows were milked four times daily to d 51 postpartum. Sows either maintained their...

Deficiency or abnormality of coagulation factor VIII (FVIII) causes a bleeding disorder called hemophilia A. Treatment involves FVIII concentrates prepared from pooled human plasma or recombinant FVIII (rFVIII) prepared from mammalian cell culture. The cost of highly purified FVIII or rFVIII is a major factor in hemophilia therapy and restricts pro...

The genotypic and phenotypic stability of four lines of transgenic pigs expressing recombinant human protein C in milk was examined. Two lines were established with a construct consisting of a 2.6 kb mouse WAP promoter and a 9.4 kb human protein C genomic DNA. Two lines were established with another construct consisting of a 4.1 kb mouse WAP promot...

We have evaluated the transgenic animal bioreactor (TAB) system for the production of human Protein C (HPC), an anticoagulant plasma protein. Mouse whey acidic protein (mWAP) gene regulatory sequences targeted expression of mWAP/HPC hybrid genes to the mammary gland of transgenic mice and pigs. The transgenes were stably transmitted through several...

Our studies in transgenic animal bioreactors sought to determine the rate limitations in posttranslational processing of recombinant human protein C (rhPC) made in mammary gland of mice and pigs. Human protein C (hPC) is a complex plasma protein containing nine gamma-carboxylated glutamic acid (gla) residues that bind calcium at about 1 to 3 mM. Ga...

Etude des consequences politiques du pragmatisme a travers l'analyse de la theorie pragmatique du droit developpee par R. Posner. Distinguant pragmatisme juridique et realisme juridique, l'A. examine la conception activiste du droit et la definition d'une jurisprudence pragmatique chez Posner, a la lumiere de la theorie judiciaire de la decision ap...

We investigated the nature of endothelin (ET) binding in the porcine ovary. We demonstrated the presence of high affinity (Kd = 0.72; 95% confidence interval = 0.43-1.1 nM) binding sites for ET-1 in the porcine ovary. The binding capacity for this ET-1-specific binding site was 97 pmol/micrograms DNA (95% confidence interval = 90-107). Autoradiogra...

We investigated the nature of endothelin (ET) binding in the porcine ovary. We demonstrated the presence of high affinity (Kd = 0.72; 95% confidence interval = 0.43-1.1 nM) binding sites for ET-1 in the porcine ovary. The binding capacity for this ET-1-specific binding site was 97 pmol/micrograms DNA (95% confidence interval = 90-107). Autoradiogra...

Twenty intact and 25 unilaterally hysterectomized-ovariectomized gilts were used to study the effect of fetal intrauterine position on conceptus development, concentrations of endogenous progesterone (P4) and estrone (E1) in the placenta and endometrium, and steroid hormone concentrations in amniotic and allantoic fluids during gestation. Gilts wer...

Intact (n = 17) and unilaterally hysterectomized-ovariectomized (UHOX, n = 19) gilts were used to study conceptus development and the steroidogenic capability of three regions of the porcine placenta under normal and crowded intrauterine conditions. Gilts were hysterectomized on either Days 30, 50, 70, or 90 of gestation. Placentas were combined ac...

The serious shortage of human organs available for transplantation has engendered a heightened interest in the use of animal organs (xenografts) for transplantation. However, the major barrier to successful discordant xenogeneic organ transplantation is the phenomenon of hyperacute rejection. Hyperacute rejection results from the deposition of high...

A series of experiments evaluated development of porcine zygotes microinjected with DNA in three culture media and two incubation temperatures, from postpubertal and prepubertal donors, and between zygotes injected with DNA into the pronucleus and the cytoplasm. Zygotes recovered from 36 postpubertal gilts in Exp. 1 were injected and cultured in mo...

The similar biological activity of rhPC and hPC indicates that porcine mammary gland can perform many of the processing reactions necessary for recombinant synthesis of complex human proteins and produce them at levels suitable for industrial bioreactor applications. The health of the transgenic pigs appeared unaffected by the expression of high le...

Conceptus estrogen synthesis in the pig begins with the d 11 blastocyst and continues throughout pregnancy. Estrogens have been implicated as regulators of numerous in utero events related to conceptus survival and development. Studies conducted in our laboratory indicate that progesterone (P4) production by the porcine placenta increases steadily...

Crossbred gilts and sows (n=116) were used for the collection of 1-cell zygotes for DNA microinjection and transfer. Retrospectively, estrus synchronization and superovulation schemes were evaluated to assess practicality for zygote collection. Four synchronization and superovulation procedures were used: 1) sows were observed for natural estrous b...

The effect of pronuclear microinjection of DNA and culture in excised mouse oviducts on the development of porcine zygotes was assessed in this study. Precocious ovulation was induced in prepubertal gilts with pregnant mare's serum gonadotrophin and hCG. Zygotes received either pronuclear microinjection of buffer alone, buffer containing a DNA cons...

Attempts to prevent prenatal harm have led to a number of court cases resulting in interference with pregnant women. These include incarceration and the imposition of medical and surgical treatments thought to prevent prenatal harm. We argue that the legal sanctions that have been used and/or are proposed for use against pregnant women in order to...

Two experiments were conducted to determine the effects of pregnenolone (P5), cyclic adenosine monophosphate (cAMP), and human chorionic gonadotropin (hCG) on porcine placental and endometrial production of progesterone (P4) and estrone (E1) in vitro at days 30, 60 and 90 of gestation. Placental P4 production increased between days 30 and 90 and wa...

In vitro release of progesterone (P4) and estrone (E1) by the porcine placenta was characterized at 12 days of gestation between d 20 and 110. Placental P4 rose linearly from d 25 to 40, plateaued between d 40 and 50, continued to increase to a peak concentration at d 100, then decreased sharply to d 110. Placental E1 decreased abruptly from d 30 t...

Nine crossbred gilts were surgically fitted with indwelling anterior vena cava cannulae, and randomly assigned to receive intramuscular injections of either 2.2 micrograms biotin/kg body wt, 6.6 micrograms biotin/kg body wt or a sham dose of carrier medium. Plasma biotin concentrations (PBC) were determined from blood samples taken at 39 time point...

Two experiments were conducted to determine efficacy of a discontinuous bovine serum albumin (BSA) gradient for isolating viable porcine spermatozoa more tolerant to 5-d liquid storage in Beltsville Thawing Solution (BTS) at 15 degrees C. The gradient, contained in a 500-ml separatory funnel, consisted of 4% BSA (60 ml) over 10% BSA (60 ml). Sperma...

This study was conducted to determine the efficacy of isolating intact, highly-motile porcine spermatozoa using a discontinuous bovine serum albumin (BSA) gradient. Either 0.25, 0.5, 1, 2.5 or 5x10(9) spermatozoa extended to 26 ml with Kiev extender were layered on a discontinuous BSA gradient (4% BSA over 10% BSA) contained within a 500-ml separat...

A total of 166 crossbred gilts weighing approximately 87 +/- 1 kg was limit-fed (2.5 kg/d) a corn-soybean meal gestation diet containing either 0 or 220 ppm of chlortetracycline (CTC) from 157 +/- 1 d of age until 15 d after breeding. These gilts were slaughtered at 31 +/- 1 or 71 d +/- 1 d of gestation for evaluation of reproductive performance. A...

A positive association (P < 0.01) was detected between estrone sulfate (ES) concentrations in maternal plasma at Day 30 of pregnancy and litter size at parturition in swine. This relationship was best described by a fifth order regression equation (R(2) = 0.5) which indicated that as ES increased from 1 to 7.5 ng/ml on Day 30, litter size increased...

The effects of reduced energy intake (ad libitum and 75% of ad libitum) and elevated mineral-vitamin intake (100 and 150% of NAS-NRC daily recommendations) on foot and leg development, incidence and severity of toe lesions, structural soundness scores and feedlot performance were studied in crossbred boars from 35 to 330 days of age (295 days on te...

Crossbred boars (35 days of age) were assigned in a 2 × 2 factorial arrangement to dietary energy (ad libitum and 75% of ad libitum) and mineral-vitamin (100 and 150% of National Academy of Sciences-National Research Council (NAS-NRC 1979) recommendation) intakes to determine the effects on metacarpal and metatarsal dimensional and mechanical chara...

Three trials, utilizing a total of 240 crossbred gilts, were conducted to study the influence of 0 (NB) or 220 (SB) microgram supplemental biotin/kg of diet on feedlot performance, plasma biotin and development of toe lesions in developing gilts. Corn-soybean meal diets were fed from weaning to 92 kg body weight. Gilts were housed on expanded-metal...

Data from 116 females previously fed a corn-soybean basal diet with 0 or 220 micrograms supplemental biotin/kg during growth and development were used to study the influence of 0 (NB) or 440 (SB) micrograms of supplemental biotin/kg to corn-(C) or wheat-(W) based diets for gilts and sows housed in total confinement. Reproductive performance through...

The influence of supplementing 0 (NB) or 440 (SB) micrograms biotin/kg to corn- or wheat-based diets on toe lesions, hair characteristics and structural soundness in 116 crossbred female swine was studied from selection (100 kg) until completion of four parities. Gilts that had been previously fed corn-soybean meal diets with 0 or 220 micrograms su...

Boars were assigned at 5 wk of age in a 2 X 2 factorial arrangement to two energy (ad libitum and 75% of ad libitum) and two Ca and P levels (100 and 150% of the National Research Council daily recommended amounts) to determine the effect of reduced growth rate and elevated Ca and P intake on foot and leg measurements, pad and horn incidence and se...

Eighty crossbred boars were utilized in a 2 X 2 factorial arrangement of two energy levels (ad libitum and 75% ad libitum) and two Ca/P levels (100 and 150% of National Research Council daily requirement) to determine the effect of varying growth rate and Ca/P intake on performance and bone characteristics throughout the growth phase. Boars were fe...

Administration of exogenous progesterone (0-55 mg/kg live weight) and oestrone (0-275μg/kg live weight) during various discrete intervals between days 4 and 30 of gestation elicited variable results depending upon the time and duration of administration. Administration of the combined steroids early in gestation (days 4 to 20, trial 1; days 4 to 12...

Administration of progesterone (P4, .55 mg/kg) and estrone (E1, .275 micrograms/kg) during discrete periods in early gestation was found to have beneficial effects on conceptus development in gilts. Three trials were conducted, with each trial examining two hormone treatment groups and one control group. In all trials, P4-E1 supplementation for eit...

Three groups of 96 crossbred gilts were weaned at 4 to 5 wk of age (average initial weight, 7.2 kg) and assigned to four dietary treatments in a 2 X 2 factorial arrangement of treatments (ad libitum vs 75% ad libitum and 100 vs 150% of NRC daily Ca and P). The effects of dietary treatments on the gait characteristics of gilts were analyzed by 16-mm...

Eighteen purebred Yorkshire boars, reared outdoors on concrete, were randomly assigned in equal numbers to three age groups (150+/-7, 200+/-7 and 250+/-7 days of age) for the purpose of examining endogenous testosterone concentrations over a 24-hr period. Blood was obtained at 30-min intervals for 24 hr, and plasma testosterone concentrations were...

Three groups of 96 crossbred gilts each were weaned at 4 to 5 wk of age (avg wt, 7.2 kg) and assigned to four treatments in a 2 X 2 factorial arrangement (ad libitum vs 75% of ad libitum energy intake and 100 vs 150% of NRC-recommended daily Ca and P). The effects on feedlot performance and on foot and leg scores and measurements were examined at a...

Forty-four purebred Yorkshire boars, reared outdoors on concrete, were randomly assigned to one of three age groups (150 +/- 7, 200 +/- or 250 +/- 7 days of age) for the purpose of examining endogenous testosterone concentration in response to one of four exogenously administered treatments. Four boars from each age group were administered either h...

Two experiments were conducted to evaluate the effects of applied heat (greater than or equal to 28 C) and crowding (less than or equal to .9 m2 floor space/animal) stress for 50 days during mid-gestation on glucocorticoid concentrations, corticosteroid binding globulin (CBG) characteristics and reproductive performance of 20 sows (Exp. 1) and 23 g...

Two trials were conducted to evaluate the effectiveness of a synthetic progestogen, allyl trenbolone, for control of estrus and ovulation in gilts. Estrus was effectively synchronized with 33 of 38 gilts exhibiting estrus 2 to 7 days after last progestogen feeding. There was no effect on fertilization rate in gilts free of ovarian abnormalities. Ov...

Summary Three series of trials were conducted to compare performance of 21- to 28-day-old weaned pigs housed in triple deck cages. The first set of trials compared the performance of pigs housed six, eight and 10 to a cage (.25, .18 and . 15 m 2 of floor space per pig, respectively). The second set examined the performances of animals housed in cag...

The purpose of this study was to examine the effects of stress induced physiological changes in the gestating sow on postnatal sexual and endocrine development of male offspring. Ten boars, ranging from 160 to 185 days of age, were randomly chosen from sows which had been maintained under either stress or control conditions during mid-gestation. Bl...

The effects of type of housing (outdoors on earth v. confinement on concrete) and system of rearing (single v. group) on age at puberty and expression of libido in boars were examined. Boars kept on earth lots and reared in groups reached puberty earlier and demonstrated greater sexual aggressiveness compared with contemporary boars maintained unde...

SUMMARY Conceptus (placental membranes, fetal fluids and fetus) development in intact control (IC) and unilaterally hysterectomized-ovariecto- mized (UHOX) gilts was characterized between days 20 and 100 of gestation to evaluate the effects of intra-uterine crowding in UHOX gilts having essentially the same number of potential embryos, but only one...